Drive mechanism for cleaning-air tubes in self-cleaning filters



July 4, 1950 Filed April 27, 1949 W. W. M NAMARA DRIVE MECHANISM FOR CLEANING-AIR TUBES IN SELF-CLEANING FILTERS 2 Sheets-Sheet 1 Z 5 INVENTOR.

July 4, 1950 w, w. MONAMARA 2,513,420

DRIVE MECHANISM FOR CLEANING-AIR TUBES IN SELF-CLEANING FILTERS Filed April 27, 1949 2 Sheets-Sheet 2 Patented July 4, 1950 DRIVE" MECHANISM FQRfiGIJEANING-AIR I TUBES IN SELF-(3LltAlIIhl'Gr EII3'1ERS.

William. WnMcNamara, Union, N;J.;assignor .t'o.

Pulverizi'ng Machinery, Company... Summit," N. J., a corporation of Newflersey" Applica-tiOmApritZ'l, 1949;Serial N0-;*89,88'6

(curse-1:61)

6 Claims. 11

This invention relates todrive mechanism-for cleanings-air. tubes in self-cleaning filters oft-the type in which the'airx' to"be.-filtered. -passes. outward-1y. through a layernf suitablemater-ial; usu

ally ;felt. Usually; the filtering: materialwis .cy-

lindrical in "form, in l-which case :the-cleaning-air tube is ring-shaped. For conveniencethe inventionwill be described assappliedto a1 cylindrical filter with a ring-shaped.cleaningeair./tube;usually' termed a blow-ring. It ish-not intended thereby to restrict Y the lscopewof the invention to filters ofthat particular.construction The blow-ring.is slotted-or' perforated .on its inner 'side where it-contacts the-ltube. so-.that-.=by supplying compressed.- air to the ring .such air can be forced inwardly through the ielh-from-the outside to? clean the-felt. To: prevent; lateral escape'of the cleaning ,air; the blow-ring.is made of-:slightly smaller diameter. than the :filter -cyie inder' so that, due to the internalrairtpressure in the cylinder, thelfilter materialaistpressed out, wardly against the'blow-ring;

The filter cylinder is vertically arranged. with a hopper attached to itslower end-tor theacollection of the separated -dust.- Thebloweri-ng is reciprocated up and down the outside- -iof-; the filter cylinder "to: keepvthe. latter; permeable. to air. Chains have been used-as adrive forreciprocating 'thering. These chains are-tendless and:- passover sprocketstopandbottom: One

' between the twoflights'of the chainbetween the sprockets. Consequently; the member,...except.at its top and bottom positions,. is .at an. acuteangle to the chain. The result is that whenthemember is pushing the ring downwards, there. is a tendency for the memberto push thechain laterally outwards and .the ring laterally inthc other direction. By providing vertical guides for the ring, lateral movement of thelattercan be avoided. The degree to which the chain moves laterally depends 'onits tension so thatethe greater its tension, the less it is deflected Ill The thrust of the chain .onthe. blow-ring is not .in. line with. the :chain. in adirection at; right angles to the plane of the chain for the reason that-.thechain. exerts .pressureon the connecting member: through. a .pin extending laterally from one of the links of the chain. There is, accordingly, annnbalanced. force on. the pin and/the link to which .itis'attachedtending to cant such linksandhthose. adjacent thereto. Such. canting resultsin wearing. the teeth .onthe sprockets so that they become-.sharp-pointed, a. condition commonlyreferredto.as. .sharks teeth.' The greater. the tension ontthe. driving chain, the less the tendency ofthe connectingmemberto cant the Jinks of the driving... chain sideways adjacent-the point at iwhichthe connecting .mem- .benz-is attachedthereto.

Anotherrmethod. of. correcting this tendency is basedr-ronrthe. ,fact. that, where. the ring. runs up anda-dowrt between guides-the lower end. of the connecting member, due to its connection to the ring is-restrainedto travel in a substantially fixed-1vertical linespaced a .fairlyconstant distance fromthe-plane of the chain. Ifthe upper "end-50f the-connectingmember is pivotally connectedtothe-pin.attached tothe chain 50. that such end cannot move axially with respect to suchcpin the-upper-end of the connecting memfber is;.-restrained bythe-chain to'travel ina plane iparalleltot-that of the .-chain-. Where the ring is free to *move laterally to a considerable degree, the-connecting:member can be held vertical by pneviding a :broad,=bearing surface between the innen; the: ring; and the. lower end of the conneetingrmember;

Withboththe upper-end oi the connecting members and-the chainmoving-in parallel planes, -the-onlyzpossible.-movemen-t.-.is a rocking one between therpinandthe chain' link towhich it is attached? with respect to-the upper end of the member inia :plane perpendicular to the plane of the: chain; This; rocking-movement may be prevented lrbyproviding a wide-bearing surface between the .PiILrOI" a part. carried thereby and the upper end nf the' connecting =member: By such-:means-the pin, is held perpendicular to the 1 plane 10ft the'chain so: that there is no r canting of the-=chainr=link to=-which* the pin is attached.

Under such conditions the wear on the sprockets and. chain is .evenlydistributed.

Best'practiceris to use both; methods, i. e.', suitablel-tension inthe chain. and a broadtbearing surface on..the member which connects'the connecting..member:- to theichain.

I have .foundtthat -the. requisite tension can dust-laden air isforced by a blower ll of stroke of the ring must equal the distance from the top of theupper sprocket to the bottom of the lower sprocket. Consequently, if the ring at the top of its upstroke is below the uppen sprocket, at the bottom of its downstroke the ring will be below the lower sprocket. This means. a

. that the connecting member must be connected to the ring in such a mannerthat the latter can greater distance than the diameter of the sprocket, so that the frame surrounds the chain U-shaped bracket comprising side members 25 and a central part 26 which serves as a guide shoe. Lugs 21 engage the two sides of a guide rail 28. The lower sprocket I! is mountedon a pedestal and the side members 25 are spaced apart more widely than the diameter of the sprockets and the two parts of the chain I 8 so thatth'e ring can move'from position X to position Z (Fig. 2).

The lower sprocket I1 is mounted on a stub shaft 39 extending laterally from the top of a j, support consisting of rod 3| slidably mounted in move up and down past the] lower sprocket; Conveniently this is accomplished by mountin the lower sprocket on a pedestal and attaching to the ring a U-shaped frame, the arms of which? are attached to the ring and are spaced apart a One form of construction is illustrated, by way of example, in the accompanying drawings,

wherein Fig. 1 is a side elevation of a self-cleaning fi ter embodying the present improvements;

Figs. 2 and 3 are diagrammatic views showing the effect of slackness in the driving chain on the down and up strokes, respectively;

Fig.4 is a side elevation on an enlarged scale of the blow-ring bracket, connecting member,

lower sprocket, and adjacent parts; ,and

Fig.5 is a section on the line 5-5 of Fig. 4.

The filter comprises a felt tube It into which rounding the tube is a cleaning-air ring I2'supplied with compressed air by a flexible pipe l3 and compressor l4. Across the top of the filter is a shaft l5 at each end of which is a sprocket Hi. This shaft is driven by the same motor which drives the compressor l4. Below each sprocket IE5 of the member to the chain and X the point of attachment to the ring. If the chain were perfectly taut, then on the downstroke the member would assume the position BY. As, however,

there is always some slack or give in the chain, the member will be in a position such as CY. If the chain is slack enough to allow the member to move into position DY, then the member will swing around to EY when it will pull instead of push. As the ring moves downward, it finally reaches the point Z or the length of the link FZ below the bottom of the lower sprocket.

It will be noted that X, Y and Z are all along the same straight line. That is due to the fact that the ring or the frame which carries it runs in vertical guides which prevent the'ring being pushed laterally by the thrust of the member On the upstroke the connecting member is pulling, not pushing, so that the chain is pulled inwards to the dotted line position, instead of being pushed outwards, as on the downstroke.

As shown in Figs. 4 and 5, the blow-ring or cleaning-air ring has attached to each side a a vertical tubular pedestal 32. On this rod is a key 33 which engages a keyway 34 to prevent 15' the rod turning. The bore of the lower part of the pedestal is enlarged to receive the upper end of a spring 35. The lower end of the spring bears against a nut 36. In assembling the drive mechanism, the chain is put around the sprockets and nut 36 is turned first until the slack is taken out-of the chain I8 and then until the spring is under predetermined tension, as indicated by the distance S. It will be noted that so long as S is three inches or other predetermined value, the tension in the chain l8 will have the desired value independently of the absolute position of the sprocket ll.

In one installation the filter may be of one height and of a different height in another. This involves difi erences in chain lengths, etc. Devi-ations from standard are taken care of by the fact that turningthe nut 36 takes up any slack in the chain due to constructional variations before any tension is placed on the chain by the compression of the spring 35. Comparison of Figs; Zand 3 shows that, when pushing, the angle down and pull up instead of pull down and push up, since the weight of the ring aids downward, but hinders upward, movement.

To avoid too great an angle between the connecting member and the vertical, the length of the connecting member should not be much less than twice the diameter of the sprockets. Also the tension in the chain should be so proportioned to the frictional drag of the ring on the felt tube and the weight of the ring that the maximum lateral deflection of the driving chain from the vertical is not much more than onequarter of the length of the connecting member on either the up or down stroke.

I'have found that for a filter bag '7 feet long a satisfactory tension for the spring 35 is around 200 lbs. For longer bags a higher tension is desirable, unless the connecting member is increased in length proportionately. If that is not done, the connecting member may pass from position YC to YD and then to YE.

In the upper ends of the rigid connecting members H! are journalled bearing members 40 each secured to the chain by two pins 4|, as shown in Fig. 4. The mutual bearing surfaces of said bearing members and said connecting members are wide enough to prevent relative canting of the two members. i

I claim:

1. A self-cleaning air filter, comprising a filter frame, a vertical filter layer carried by such frame, a cleaning-air tube pressed against said filter layer, a pair of sprockets on either side of said filter layer, one vertically over the other, an endless chain passing around each pair of sprockets; means for driving one of each pair of sprockets continuously in the same direction, a slidable support for the idle sprocket of each pair, a spring acting on said support to place the chain under tension, and rigid connecting members between the chains and the tube, whereby as the chains move around said sprockets they reciprocate said tube up and down the filter layer.

2. A self-cleaning air filter as in claim 1, in which the connecting members have a length not less than twice the diameter of the sprockets and the tension in the chain is such that the maximum lateral deflection of the chains during operation of the filter is not more than onequarter of the length of the connecting members.

3. A self-cleaning air filter, comprising a filter frame, a vertical filter layer carried by such frame, a cleaning-air tube pressed against said filter layer, a pair of sprockets on either side of said filter layer, one vertically over the other, one sprocket being driven continuously in the same direction and the other being idle, an endless chain passing around each pair of sprockets, vertical guides for the cleaning-air tube adapted to restrain lateral movement of the latter, a pair of rigid connecting members each pivotally connected at one end to the cleaning-air tube and at the other end to a link of one of said chains whereby as the chains move around said sprockets they reciprocate the said cleaning-air tube up and down the filter layer, a slidable support for the idle sprocket of each pair permitting the distance between the sprockets to be varied, and a spring between the filter frame and said slidable support to place the chain under tension.

4. A self-cleaning air filter, comprising a filter frame, a vertical filter layer carried by such frame, a cleaning-air tube pressed against said filter layer, a, pair of sprockets on either side of said filter layer, one vertically over the other, an endless chain passing around each pair of sprockets, means for driving one of each pair of sprockets continuously in the same direction, and rigid connecting members each pivotally connected at one end to the tube, bearing members each secured to a link of one of said chains passing through the other end of said connecting member whereby as the chains move around 6 said sprockets they reciprocate the said tube up and down the filter layer, the mutual bearing surfaces of said bearing members and said connecting members being wide to prevent relative canting of the two members.

5. A filter as in claim 4, in which the chain is of the roller type and the bearing member is secured thereto by two pins passing through both the bearing member and adjacent rollers of the chain.

6. A self-cleaning air filter, comprising a filter frame, a vertical filter layer carried by such frame, a, cleaning-air tube pressed against said filter layer, a pair of sprockets on either side of said filter layer, one vertically over the other, an endless chain passing around each pair of sprockets, means for driving one of each pair of sprockets continuously in the same direction, a pair of hollow pedestals on said filter frame, each having a rod slidably mounted in its bore and projecting therefrom at both ends, each rod having one of the idle sprockets mounted on one end thereof, a spring surrounding each of said rods bearing at one end on the pedestal and at the other end on a nut on the end of said rod opposite the end carrying theidle sprocket, Whereby turning said nut first takes up the slack in the chain and then compresses the spring and thereby places the chain under tension, and rigid connecting members between the chains and the tube whereby as the chains move around said sprockets they reciprocate said tube up and down the filter layer.

WILLIAM W. McNAMARA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 488,698 Payne Dec. 2'7, 1892 2,185,079 Hall Dec. 26, 1939 2,476,942 Arnold July 19, 1949 FOREIGN PATENTS Number Country Date 255,876 Germany p Jan. 23, 1913 

